JPH08291784A - Leakage preventing device for hydraulic turbine - Google Patents

Abstract

PURPOSE: To prevent air from leaking to a drain pipe by reducing air pressure of a circumference at the time of racing of a liner. CONSTITUTION: A hydraulic turbine or a pump hydraulic turbine consists of a bypass pipe 12 for allowing the outer circumferential part of an upper cover 3 to communicate with the inner side of the seal part 9 of the upper cover 3, and a valve 13 arranged in the bypass pipe 12. Pressure in the outer circumferential part of a liner is reduced so as to prevent air from entering a drain pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prevention of leakage of push-down air to the downstream side of a suction pipe when a runner idles during phase-shifting operation or standby operation of a water turbine or a pump turbine.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG. FIG. 2 is a view showing a state of a conventional turbine or pump turbine when the runner idles. In the figure, 1 is a runner, 2 is a runner cone, 3 is an upper cover, 4 is a lower cover, 5 is a suction pipe, 6 is a guide vane, 7 is an air supply / exhaust pipe opened to the upper cover, 8 is a main shaft, and 9 is The seal portion 10 is a drain pipe that connects the lower cover to the suction pipe.

The operation of the conventional example will be described. When performing the phase-matching operation of the water turbine or the pump water turbine or starting the pump of the pump water turbine, as shown in FIG. 2, the guide vane 6 is fully closed and compressed air is sent from the air supply / exhaust pipe 7 to the water of the runner 1 part. The runner 1 was rotated idly by pushing down to hold the water surface at the position of the water surface A where the water surface does not hit the runner 1, and the torque required for idling the runner 1 was reduced. Compressed air is required to push down the water surface because the runner 1 is generally installed below the water level of the lower dam in order to prevent cavitation occurring in the runner 1 in a water turbine or a pump turbine.

In this state, when the runner 1 idles to start a steady phase-adjustment operation, a wave having a large wavelength is excited on the water surface pushed down by the swirling flow of air in the suction pipe 5 due to the idling, and the state of the water surface is shown in FIG. Changes from water surface A to water surface B.
A and B are the water surface.

[0005]

In the phase-matching operation of the conventional turbine or pump turbine, when the pushed water surface position water surface A is not sufficiently low, when the water surface becomes the water surface B, the runner 1 is brought to the water surface B. Come into contact with each other, causing large torque fluctuations and spindle vibration. On the other hand, when the pushed water surface position is too low, the water surface B contacts the bent portion of the suction pipe 5, and compressed air leaks to the rear of the suction pipe 5.

Therefore, it is necessary to keep the position of the pushed-down water surface at an appropriate position in consideration of the above, and to prevent the lower cover 4 from leaking water from the guide vanes 6 around the runner 1 and increasing the idling force. A drainage pipe 10 is provided for cleaning. In order to simplify the structure of the lower cover 4 and increase the economical efficiency, the drain pipe 10 is directly opened to the lower cover 4 as shown in FIG. The outlet of the drainage pipe opens to the underwater portion of the lower portion of the suction pipe 5. The reason why the water is opened in this way is that the drainage is ejected when it is discharged to the aerial part, and this water is wound up toward the runner 1 at the upper side and collected again on the outer peripheral portion of the runner 1 and the drainage is not sufficiently performed. is there.

Since recent runners have been designed to have a high head and a high speed, the peripheral speed of the runner 1 is increased and the pressure around the runner is higher than before. Therefore, the pressure of the air around the runner 1 on the outer periphery of the seal portion 9 receiving the supply of the seal water becomes larger than the water level difference Hs shown in FIG. 2, and the air is mixed at the inlet portion of the drain pipe 10. A situation occurs in which this air leaks to the rear of the suction pipe 5 through the drain pipe 10.

Therefore, conventionally, there has been a problem that a large amount of compressed air and equipment therefor are required to make up for leaks. Regarding leakage, the valve in the middle of the drainage pipe was throttled to reduce leakage, but there was a problem that the amount of drainage also decreased at the same time.

An object of the present invention is to provide an air leak prevention device for a water turbine that reduces the air pressure around the runner when it is idling and prevents air from leaking to the drain pipe.

[0010]

SUMMARY OF THE INVENTION In a turbine or a pump turbine, a leakage preventing device for a turbine according to the present invention comprises an outer peripheral portion of an upper cover 3 and a secondary back pressure portion (inside a seal portion) of the upper cover. It is characterized in that it is composed of a bypass pipe 12 that communicates with a valve 13 provided in the bypass pipe.

[0011]

The pressure on the outer peripheral portion of the upper cover 3 passes through the bypass pipe 12 through the valve 13 and passes through the secondary back pressure portion to descend, and air is mixed into the drain pipe 10 and leaks to the rear of the suction pipe 5. Prevent.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of a leakage prevention device for a water turbine according to a first embodiment of the present invention. In the figure, 1 is a runner, 2 is a runner cone, 3 is an upper cover, 4 is a lower cover, 5 is a suction pipe, 6 is a guide vane, 7 is a supply / exhaust pipe, 8 is a main shaft, 9 is a seal portion, 10 is a drain pipe. , 11 are balance holes, 12
Is a bypass pipe and the outer peripheral portion of the runner of the upper cover 3 and the seal portion 9
Communicate with the inside of. Reference numeral 13 is a valve provided in the bypass pipe 12. A and B are the water surface.

The operation of the first embodiment will be described. FIG. 1 shows a situation where the runner 1 is idling by pushing down the water surface.
At this time, water leakage from the fully closed guide vanes 6 is accumulated in the outer periphery of the runner 1 while being subjected to centrifugal action in a shape as shown in the figure, and the water surface in the suction pipe 5 is waved in a state like the water surface B. It has occurred. In this state, the valve 13 is fully opened, and the air part on the upper cover 3 side of the outer peripheral part of the runner 1 and the air part in the suction pipe 5 are bypass pipe 12 and balance hole 11
Is communicated by. Therefore, the air pressure in the outer peripheral portion of the runner 1 becomes substantially equal to the pressure in the suction pipe 5, and the runner 1
Since the air in the outer peripheral portion of the air flows out to the suction pipe 5 through the drain pipe 10 and lowers the water surface, the pressurized air is not wasted.

[0014]

By providing a bypass pipe to connect the air portion on the upper cover side of the outer peripheral portion of the runner and the secondary back pressure portion of the runner on the upper cover, almost only the air can balance the bypass pipe and the runner balance hole. By circulating the air, the pressures of both the air portion on the upper cover side of the outer peripheral portion of the runner and the air portion in the suction pipe are made substantially equal. This effect lowers the pressure on the outer periphery of the runner and prevents air from mixing into the drain pipe, preventing air from leaking through the drain pipe to the rear of the suction pipe, ensuring stable idle operation. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a leakage prevention device for a water turbine according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a state of a conventional turbine or pump turbine when the runner idles.

[Explanation of symbols]

1 ... runner, 2 ... runner cone, 3 ... upper cover, 4 ... lower cover, 5 ... suction pipe, 6 ... guide vane, 7 ... supply / exhaust pipe, 8 ... spindle, 9 ... seal part, 10 ... drain pipe, 11 ... Balance hole, 12 ... Bypass pipe, 13 ... Valve, A, B ...
Water surface, Hs ... Water level difference.

Claims (1)

[Claims] 1. A bypass pipe (12) for communicating an outer peripheral portion of an upper cover (3) with a secondary back pressure portion (inside a seal portion) of the upper cover in a water turbine or a pump turbine, and the bypass pipe. And a valve (13) provided on the water turbine.